I was wondering if this needs the branded gas they sell online or if I can get by with what I have access to at the local big box? If so I'll just buy something locally, I just know some of you guys love the iwatani.

I've used both the Iwatani branded and a generic brand butane can. Although the Iwatani can seems to provide a more consistent, stable flame (the flame can pulse occasionally when the torch is pointed at extreme angles, e.g. vertically down or steeper), the generic butane can worked fine. I believe the model is BU-6; the most important thing is that the ring where the torch connects to has a notch cut out of the ring for the torch to snap into.

Most asian markets should have these butane cans; they're used for portable/tabletop butane burners that are sold at most asian markets.